"""A generally useful event scheduler class.

Each instance of this class manages its own queue.
No multi-threading is implied; you are supposed to hack that
yourself, or use a single instance per application.

Each instance is parametrized with two functions, one that is
supposed to return the current time, one that is supposed to
implement a delay.  You can implement real-time scheduling by
substituting time and sleep from built-in module time, or you can
implement simulated time by writing your own functions.  This can
also be used to integrate scheduling with STDWIN events; the delay
function is allowed to modify the queue.  Time can be expressed as
integers or floating point numbers, as long as it is consistent.

Events are specified by tuples (time, priority, action, argument).
As in UNIX, lower priority numbers mean higher priority; in this
way the queue can be maintained as a priority queue.  Execution of the
event means calling the action function, passing it the argument
sequence in "argument" (remember that in Python, multiple function
arguments are be packed in a sequence).
The action function may be an instance method so it
has another way to reference private data (besides global variables).
"""

# XXX The timefunc and delayfunc should have been defined as methods
# XXX so you can define new kinds of schedulers using subclassing
# XXX instead of having to define a module or class just to hold
# XXX the global state of your particular time and delay functions.

import heapq
import Event
import Handle
import time
#import logging
from Log import logger
from collections import namedtuple
from Lock import Wakeup_Lock

#log initialization
#logger = logging.getLogger('whu_sched')
#hdlr = logging.FileHandler('/var/tmp/whu_sched.log')
#formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
#hdlr.setFormatter(formatter)
#logger.addHandler(hdlr)
#logger.setLevel(logging.DEBUG)

__all__ = ["scheduler"]
Event = namedtuple('Event', 'time, priority, handle, argument, uid, description')

class scheduler:

  _queue = []
  
  def __init__(self, timefunc, delayfunc):
    """Initialize a new instance, passing the time and delay
    functions"""
    
    self.timefunc = timefunc
    self.delayfunc = delayfunc

  def enterabs(self, time, priority, action, argument, uid,description):
    """Enter a new event in the queue at an absolute time.

    Returns an ID for the event which can be used to remove it,
    if necessary.

    """
    event = Event(time, priority, action, argument, uid,description)
    heapq.heappush(scheduler._queue, event)
    return event # The ID

  def enter(self, delay, priority, action, argument, uid,description):
    """A variant that specifies the time as a relative time.

    This is actually the more commonly used interface.

    """
    time = self.timefunc() + delay
    return self.enterabs(time, priority, action, argument, uid,description)

  def cancel(self, event_id):
    """Remove an event from the queue.

    This must be presented the ID as returned by enter().
    If the event is not in the queue, this raises ValueError.

    """
    i=0
    deleted = False
    global logger
    print 'event ', event_id,' to be canceled\n'
    while i < len(scheduler._queue):
      #print i,'th event in queue is',scheduler._queue[i][4]
      if scheduler._queue[i][4]==int(event_id):
        print 'event ',event_id,' is queuing\n'
        #time.sleep(3) #might cause a problem of inconsistency
        #should try and catch
        scheduler._queue.remove(scheduler._queue[i]) 
        deleted = True
        break
      i = i+1
    if deleted:
      msg = 'Successfully canceld event %s'
      logger.debug(msg,event_id)
      scheduler.print_queue()
      heapq.heapify(scheduler._queue)
    else:
      msg = 'fail to cancel event %s'
      logger.error(msg,event_id)
      print msg %event_id
    return deleted

  def empty(self):
    """Check whether the queue is empty."""
    return not scheduler._queue

  def run(self):
    """Execute events until the queue is empty.

    When there is a positive delay until the first event, the
    delay function is called and the event is left in the queue;
    otherwise, the event is removed from the queue and executed
    (its action function is called, passing it the argument).  If
    the delay function returns prematurely, it is simply
    restarted.

    It is legal for both the delay function and the action
    function to modify the queue or to raise an exception;
    exceptions are not caught but the scheduler's state remains
    well-defined so run() may be called again.

    A questionable hack is added to allow other threads to run:
    just after an event is executed, a delay of 0 is executed, to
    avoid monopolizing the CPU when other threads are also
    runnable.

    """
    # localize variable access to minimize overhead
    # and to improve thread safety
    q = scheduler._queue
    delayfunc = self.delayfunc
    timefunc = self.timefunc
    pop = heapq.heappop
    global logger
    def print_empty():
        print 'empty'
    
    while q:
        scheduler.print_queue_id()
        if len(q)==0:
    	  print 'Empty queue\n'
          self.enter(1,10,print_empty,(),99999,'kkk')
        checked_event = q[0]
        time, priority, action, argument,uid,description = checked_event
        now = timefunc()
        if time > now:
          Wakeup_Lock().CloseLock()
        while time > now and Wakeup_Lock().IsLocked():
          now = timefunc()
          delayfunc(1)
          #print 'event %s handle %s description %s Sleeping\n' %(uid,action,description)
        else:
    	  if Wakeup_Lock().IsLocked():
    	    Wakeup_Lock().OpenLock()
          event = pop(q)
            # Verify that the event was not removed or altered
            # by another thread after we last looked at q[0].
          if event is not checked_event and event[5] == 'URG':
    	    msg = 'Urgent event %s  arrived'
    	    logger.debug(msg,event[4])
    	    logger.info("event %s %s called with args: %s",event[4],event[2],event[3])
            event[2](*event[3])
            delayfunc(0)   # Let other threads run
    	  elif event is checked_event:
    	    logger.info("event %s %s called with args: %s",uid,action,argument)
            action(*argument)
            delayfunc(0)   # Let other threads run
          else:
            heapq.heappush(q, event)
    print 'Empty Queue'

  def reset(self):

    event =Event(1,0,Handle.H_Init().handle,(),0,'NEWINIT')
    scheduler._queue = [event]
    print 'Queue reset\n'

  def urgent(self,event_id):

    global logger
    msg = "Try to elevate event %s to urgent"
    i = 0
    while i<len(scheduler._queue): 
      if scheduler._queue[i][4] == int(event_id):
        break;
      else:
        i += 1
    if i == len(scheduler._queue):
      err = 'Can not find event %s'
      logger.error(err,event_id)
      print err %event_id
      return False 
    else:  
      (tmp,tmp,handle,argument,uid,tmp) = scheduler._queue[i]
      scheduler._queue.remove(scheduler._queue[i]) 
      event = Event(0,0,handle,argument,uid,'URG')
      heapq.heappush(scheduler._queue,event)
      if Wakeup_Lock().IsLocked():
        Wakeup_Lock().OpenLock()
      print 'after urgent insert\n'
      i = 0
      while i < len(scheduler._queue):
        print i,'th event in queue is',scheduler._queue[i][4]
        i +=1
      #time.sleep(5)
      logger.debug(msg,event_id)
      print msg %event_id
      return True

  @staticmethod
  def print_queue():

    i =0
    print '<=================================>\n'
    while i<len(scheduler._queue):  
      print scheduler._queue[i]
      i +=1
    print '<=================================>\n'

  @staticmethod
  def print_queue_id():

    i = 0
    print '<=================================>\n'
    while i<len(scheduler._queue):  
      print '_queue[%i] is event %i\n' %(i,scheduler._queue[i][4])
      i +=1
    print '<=================================>\n'

  @property
  def queue(self):
    """An ordered list of upcoming events.

    Events are named tuples with fields for:
        time, priority, action, arguments

    """
    # Use heapq to sort the queue rather than using 'sorted(self._queue)'.
    # With heapq, two events scheduled at the same time will show in
    # the actual order they would be retrieved.
    events = scheduler._queue[:]
    return map(heapq.heappop, [events]*len(events))
  
  def wakeup(self,event):
    """This function is used to wakeup an event,
     Events are named tuples with fields for:
        time, priority, action, arguments
    """
    self.cancel(event)
    priority,action,argument = event[1:]
    self.enter(0,priority,action,argument)
